I am using SP3. When i try to intall realtek HD audio drivers the installer program tells me "install failed" and exits. Looking in device manager shows that i have no drivers installed. Its really annoying. SoundBlaster 16 was easier to get working!
The problem is that the MS Universal Audio Architecture (UAA) High Definition Audio also known as HD Bus drivers are either not isntalled or corrupt. Since i am running SP3, they are suppose to be there, so there is something wrong with them.
Step 1: Go into installed programs and uninstall the HD audio drivers. (if they are not there go to step 2) It will complain that a bunch of stuff will probably stop working if you do this. Ignore this warning, and all like it. I mean, who cares if some stuff breaks a little, you just want a 'multimedia PC in 2009'!
Step 2: Reboot your computer, You will need to reinstall the HD bus, the installer for that is called KB888111 and can be gotten here. Now, since you have service pack 3, you wont be able to install these, because windows thinks that you already have them. You need to trick windows into thinking you have SP2:
Step 3: Get into regedit (google it) and edit the following key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Windows\CSDVERSION
Set it to 00000200 from 00000300. Restart windows.
Step 4: Install KB888111, install your audio drivers. Reboot. Change the above key back to 00000300 (or dont like me, i mean, who cares?).
If this does not work for you, you should just reinstall windows, or, get a real sound card. Ive never had more problems getting sound to work then with this HD audio crap.
Also, i hear this will also work for other sound cards that use this UUA crap.